A red moon will hang below a Red Planet in the night sky tonight, during a lunar eclipse that coincides with our closest approach to Mars in six years. The eclipse is expected to peak at 3:45 a.m. Tuesday morning. During a lunar eclipse, the Earth casts its shadow on the moon as it passes between the moon and the sun. This eclipse will be a total eclipse, when the moon is completely cloaked in the shadow and that will cause the moon to appear in a dramatic red colour. Lunar eclipses happen several times a year, but can only be viewed from certain places around the globe, and in most cases it is only a partial eclipse.